Method of making sliders for fasteners



Nov. 21, I933. s; E. PRENTICE 1,935,727

METHOD OF MAKING SLIDERS FOR FASTENERS Original Filed July 12, 1932 4 Sheets-Sheet 1 a zww/f 60/ Z'MW v /7?;

Nov. 21, 1933.

G. E. PRENTICE 1,935,727

METHOD OF MAKING SLIDERS FOR FASTENERS Original Filed July 12, 1932 4 Sheets-Sheet 2 fizz Nov. 21, 19,33.

. G. PRENTICE 1,935,727 METHOD OF MAKING SLIDERS FOR FASTENERS Original Filed July 12, 1932 4 Sheets-Sheet I5 NOV. 21, 1933. p c 1,935,727

METHOD OF MAKING SLIDEHS FOR FASTENERS Original Filed Jul 13, 1932 4 Sheets-Sheet 4 wzwr Patented Nov. 21, 1933 UNITED STATES METHOD OF MAKING sLIDEns FOR- FASTENERS George E. Prentice,- Berlin, Conn.

Original application July 12,. 1932, Serial No. 622,085, now Patent No. 1,900,949, dated March 14, 1933. Divided and this application August 30, 1932. Serial No. 631,054

23 Claims.

This invention relates to slide operated separable fasteners of the kind in which complemental series of mating or interlocking fastener elements are arranged along the opposite edges respectively of a gap or opening in a garment, shoe, receptacle, or other article and are moved into and out of cooperating relationship by means of a slider, and relates more particularly to a method of and apparatus useful in making an improved slider for such fasteners, the .present application being a division of my copending application, Serial No. 622,085, filed July 12, 1932, (now issued as Patent No. 1,900,949, dated March 14, 1933) which in turn is a continuation in part of my application Serial No. 562,518, filed September 12, 1931.

It has heretofore been proposed to make sliders of this character bycasting, coining, milling, etc., but none of these modes of production has thus far been found commercially satisfactory,

' partly by reason of the initial cost of production and partly on account 'of the undue weight and clumsy appearance of the finished article. For these reasons sliders are almost universally made from sheet material, but this usually necessitates reinforcement by yoke pieces, soldering, or the like to provide the strength and rigidity requisite to prevent spreading of the front and rear wings of the slider during use, all of which adds to the expense of manufacture and often results in the formation of a slider-of undesirable appearance, and when stiffening of the neck has previously been attempted, as by doubling or bending the sheet material at this point, a line of weakness, incipient crack, or actual crevice has invariably been produced, so that even though the neck might appear of adequate depth to resist separation of the wings during use, such inherent defects so reduce the effective section of the material at the neck as greatly to lessen the strength of the slider as compared with that which might be expected theoretically.

I have previously made rivetless sheet metal sliders stiifened by the provision of integral external ribs or yokes at the neck portion and am aware of other attempts to obtain the desired stilfness in a sheet metal slider as, for example, by sharply bending the metal at the neck to form a V-shapedfold constituting the divider, but

none of the prior constructions known to me meets all of the requirements of an acceptable fastener for use under all of the severe conditions to which such sliders are subjected.

The fastener units of the earlier and cruder constructions were of substantially rectangular shape, having sharp outer corners, but the more modern fastener units have rounded outer edges which not only give a better and,more finished appearance with less likelihood of scratching or otherwise injuring fine garments or the like with which they are associated, butwhich'also conduces to the smooth and free movement of the slider. Prior sliders have usually been designed with channels and separator members of a shape particularly intended to cooperate with the rectangular type of fastener unit, and in 'designing them, a considerable proportion of the normal strength of the metal has been sacrineed in stretching it to shape and in the employment of' sharp angles-and corners rather than smoothly rounded, arch-like bends adapted to use the strength of the material employed to its greatest advantage. Moreover, in many prior constructions, the pull-retaining member has been made as a separate piece of material, thus necessitating a multiplication of operations in assembling the slider. Furthermore, the means for attaching this pull-retaining member has not always been as strong as desirable, and in some cases has necessitated a sacrifice of strength in the slider body itself.

In accordance with the present invention-I provide a novel method of producing a slider which, in the preferred form, is made of a single piece of sheet material (with the exception of the pull tab), its neck being of tubular and substantially oval contour at that transverse vertical cross section at least which is midway between the wings,

. and with its longer dimension vertical so as to form a very rigid strut well adapted to resist rela--" tive movement of the slider wingsQ and which incidentally is particularly well adapted for use with fastener elements of the modern type having smoothly rounded outer ends with which it cooperates to give a smooth and easy opening and closing movement. While particularly useful with this type of fastener element, the improved slider, though perhaps to a lesser degree, adds to the smoothness of operation of the older type of fastener unit. At the same time the new slider is exceedingly rigid and stiff, utilizing the material. to the best advantage for the purpose, avoiding sharp bends, doubling, or other weakening processes, and so disposing the metal that the finished slider isfrom to 300% stronger than prior sliders of similar weight, and thus it is possible to make an acceptable slider of small size and light weight,.and at an extremely low cost, and which in external appearance is more pleasing than the usual types of slider.

The neck-portion of a slider of this character 11 remainsbetween the stringers when the fastener is closed, and as usually constructed, is of such shape that it tends to hold the stringers in widely divergent relation at the upper end of the slider so as to produce an objectionable gap beyond the end stops .when the slider is in closing position. Moreover, while the inner surface of the neckof prior sliders is usually so shaped as to perform its fastener separating function, it is not ordinarily of such contour as to facilitate the smooth and ready entry of the opposed series of fastener elements into the-respective guide channels, so that in closing the fastener unnecessary friction is engendered and the closing operation is unduly harsh. I

In accordance with the present invention I provide a slider whose neck portion preferably tapers upwardly substantially to an acute edge, as well as downwardly, so that the mouths of the guide channels substantially merge at the extreme upper end of the slider, thus permitting the opposed stringers to lie close together in substantially parallel relation beyond the end of the slider when the fastener is closed, and at the same time providing smoothly tapering throats for guiding the fastener elements into their respective channels.

Sliders of the kind in question are commonly made of a material which is resistant to corrosion from the effects of moisture, perspiration, etc, one such material, for example, being an alloy comprising approximately 64% copper, 18% nickel, and 18% zinc, such material beingknown under the trade name of 18% nickel alloy or sometimes as nickel silver". The tensile strength of this material in sheet form and in the annealed condition is in the neighborhood of 58,000 pounds per square inch, with a hardness approximating '77 Brinell; The hardness and strength of such material is greatly increased by cold working it mechanically as by folding, forging, swedging, etc. By such mechanical working the strength may arise as high as 95,000 pounds per square inch and the hardness may increase to 158 Brinell. However, it is very important to note that harsh working may result in extreme brittleness and the formation of incipient fractures.

In accordance with the preferred method of making my improved slider I employ sheet material of substantially the composition above referred to (although it is to be understood that other materials may be employed) and through out the several steps of the process seek to increase the strength of the metal by mechanical working while at the same time observing the greatest care to avoid harsh treatment such for example, as sharp bending which tends to develop lines or areas of undue hardness and brittleness or the formation of incipient cracks or fractures, and I attribute the great strength of my improved slider, as compared with prior constructions, not only to its improved structural shape, as above referred to, but in part at least to the method of conforming the original flat sheet metal blank to the shape of the completed slider body.

In thus conforming and molding the sheet metal toshape,ltakecarealwaystoconfineallparts closely between enveloping walls while changing the shape of such parts, and to produce the ultimate shape in a series of successive folding or buckling operations, while avoiding any such stretching of the metal as. to thin it, or the forms-- ticnofsharpanglesorbendsatanytimeinthe process. The metal is thus constrained to flow smoothly without disruption of its fibrous structure, but during such fiow its constituent crystals so rearrange themselves as greatly to increase the strength and hardness of the material, particularly at the neck portion of the slider where the working of the metal is most pronounced.

The improved apparatus employed in carrying out my process comprises suitable dies and adjunctive elements adapted to confine the material at substantially all points during the shaping operations, whereby at all parts to determine the fiow of the metal accurately, thus avoiding the accidental production of excessive strains at any point and compelling the material to fiow smoothly so that incipient cracks or fractures are avoided.

In the accompanying drawings in which preferred steps in and apparatus appropriate to the manufacture of my improved slider have been illustrated by way of example.

Fig. 1 is a fragmentary front elevation of a separable fastener of the class to which the present invention relates, showing the improved slider associated therewith;

Fig. 2 is a plan'view to smaller scale of a blank useful in making the improved slider;

Fig. 3 is a plan view similar to Fig. 2, but showing the blank at the end of one of the early steps in the process of making the slider;

, Fig. 3* is a section, to large scale, on line 3 -3 of Fig. 3;

Fig. 4 is an edge view of the blank at the end of a further step in the process;

Fig. 5 is a corresponding front elevation;

Fig. 6 is an edge elevation of the blank at the end of a further step in the process;

Fig. 7 is a corresponding front elevation;

Fig. 8 is an edge view of the slider just prior to the last step in the process;

4 v auJ Fig.9isaplanviewofthepartsasshownin Fig. 8;

Fig. 10 is a fragmentary section substantially on the line 10-10 of Fig. 9;

Fig. 11 is a fragmentary section to larger scale substantially on the line 11-11 of Fig. 10.

Fig. 12 is a section on-the line 12-12 of Fig. 10;

Fig. 13 is a plan view omitting the pull tab;

Fig. 14 is a fragmentary section on the line 1414 of Fig. 13;

15 is a side elevation of a pull retaining element of modified construction;

Fig. 16 is a side elevation of a slider employing the pull retaining element of Fig. 15;

Fig. 17 is a plan view of a single fastener element showing the edge of the stringerin section;

Fig. 18 is a side elevation 'of the parts shown in Fig. 17;

Fig. 19 is a front elevation, partly broken away and partly in section, showing the'cooperative relation of the neck of the improved slider with a desirable form of end stop and with the edges of the stringers of the fastener device;

Fig. 20 is a plan view of a blanking die useful in forming blanks, such as shown in Fig. 2, from a strip ofsheet material;

Fig. 21 is an end elevation of the parts shown in Fig. 20, the strip of material being shown in section;

Fig. 22 is an end elevation of a blanking punch cooperating with the die of Fig.20;

Fig. 23 is a plan view of a die user in reducing theblankofFig.2totheformshowninFig.3;

of the completed slider,-

.punch and showingthe resulting embryo 'slider in section;

Fig. 28 is a section substantially at right angles to Fig. 27;

Fig. 29 is a fragmentary enlarged elevation of the-lower end portion of the forming'punch of Fig. 28;

Fig. 30 is a plan view of a forming die for use in changing the shape of the blank from that of Fig. 5 to that of Figs. 6 and '7;

Fig. 31 is a section on the line 31-31 of Fig. 30 showing the punch, which cooperates with the die of Fig. 30, substantially at the end of its down stroke and showing the slider in vertical section;

Fig. 31 is a fragmentary elevation of the lower end portion 'of the punch shown in Fig. 31;

Fig. 31 is a section'on line 31 31 of Fig. 31;

Fig. 32 is a section on line 32-32 of Fig. 30 showing the slider in position in the die and in vertical section;

Fig.'33 is a vertical section illustrating the co-- operating die and punch which converts the embryo slider body'from the shape of Fig. 5 to that of Fi 7; i

Fig. 33* is a top view of one of the arbors of the punch shown in Fig. 33;

Fig. 34 is a vertical section illustrating a punch and die operative to give the final shape to the neck of the slider whereby to change it from a form substantially as shown in Fig. 10 to that of Fig. 14; Fig. 34* is a side elevation of one of the arbors of the die of Fig. 34;

Fig. 35 is a section substantially at right angles to that of Fig.'34;' and Figs. 36 and 3'7 are diagrams illustrating the action which I believe to be produced by indent-' ing the neck of the slider in accordance with two different methods of procedure, respectively.

Referring to the drawings, and particularly to Fig. 1, the numerals 1 and 2 indicate respectively the flexible stringer members usually employed in fastener devices of this character to support the opposed series of fastener elements. These stringers are provided, as is usual, with beaded edges 3 and 4 respectively, to which are secured the fastener units forming the opposed series 5 and 6 respectively. The stringers are united at one end of the gap by means of a stop 7, and-at the other end of the series of fastener units, stops 8 are provided for limiting the movement of the actuating slider 9. This slider, as here disclosed, is furnished with an elongate pull retaining loop 15 which passes through an opening in the pull tab 10 and which, as here shown, is elongate to permit-the pull tab to be moved-from the top tothe bottom of the slider to faciliate movement ottheslider in either direction.

upper end of the slider, as viewed in Fig. 1, is referred to as the top of the slider, and the other end is referred to as the lower or bottom end, it being understood that such reference is for case each other.

in description, and that in actual use the slider may move horizontally as well as up and down, and that the wider end of the slider may, under some conditions, be its lower end.

' The improved slider herein disclosed is preferably made from sheet material,- such as sheet metal, which offers substantial advantages, for example lightness of weight, ease of working, and capability of taking a fine finish, in the manufacture of sliders of this type. Thus, in accordance with the preferred method of manufacture, I make the slider body from a unitary blank B (Fig. 2) of sheet material which may bestamped or otherwise shaped from the sheet to provide the rear wing 12, the front wing 13 and the integral and relatively narrow neck portion 14. In the preferred construction the free end of the wing 13 is provided with an elongate integral extension or tongue 15 the central portion of which forms the pull retaining loop above described. Near its end this tongue is reduced in width forming a shoulder 16- and the narrow portion 16, the latter terminating in the enlargement or head 17.

Having provided the blank B above described, the next step in the process is to turn up the flanges 18 and 19 at the lateral margins of the rear and front wings respectively, as shown in Fig. 3, and then to fold the blank at its neck portion so as to bring the wings into substantially parallel relation, with the flanges 18 and 19 of the rear and front wings opposed to each other. Either after or concomitantly with this first folding operation the neck portion is pressed, swedged or otherwise depressed at its no central portion to form a hollow, as shown at '20 in Fig. 5,. the side walls of this hollow preferably making an angle of approximately 23 with Thereafter, the depression of the neck portion is carried further, as shown in 5 Figs. 6- and 'l, as for example by placing a suitable arbor between the wings and by employing a punchof proper shape working in unison with side' pressers'so as gradually to deepen the hollow in the'neck as the metal is folded or buckled until it takes the shape shown at 20 in Figs. 7 and 10, the angle between the side walls of the deep depending fold constituting the neck being now approximately 18 with the bend or bottom of the deep fold which forms the neck between the wings and at a point substantially below their extreme upper ends. Either subsequent to or concomitantly with these neck shaping operations, the extension strip is first bent outwardly at 21, as shown in Fig. 4, 3 and then upwardly at 22 to' form the arm 23. The pull tab is then threaded over the arm 23 and onto the part 15, and the extension is then again bent, as shown at 21 in Fig. 8,'so that the arm 23 is caused to lie in the deepened hollow or with the shoulder 16 engaging the front sun-30' face of the front wing, and the head 17 is preferably bent down to engage the rear surface of the rear wing] Having disposedthe part 16 within its socket, the neck shaping operation is then completed by swedglng the lateral marfFor convenience in further description, the

ginal portions of the neck, as shown at 24 in Fig. 14, so as smoothly to'curve the'material and to cause the opposite lateral margins of the neck substantially to meet and form an acute angle at the point 25 which thus defines the extremeupperendoftheslidentheoppositelateral portions of the neck being curved concavely towardeachothersothattheneckbecomesin effect of substantially oval tubular form inthe verticalsectionofFig.14.-

Itmaybenotedthatthe flanges18'and19,together with the front and rear wings and the neck 14, define the guide channels 26 and 27 for plane extending from front to rear'of the slider as shown at 28 in Fig. 11, forming a smoothly curved surface which is uninterrupted and integrally continous in a front to 'rear direction and which merges into the-inner surfaces of the wings 12 and 13 respectively. Moreover, the material which constitutes the neck is arched downwardly in'a plane parallel to the wingas shownin Fig. '10 and is continuously curved, smooth, and uninterrupted from one lateral margin of the neck to the other lateral margin thereof, and throughout its entire thickness, devoid of sharp angles-crevices, lines of weakness, or incipient cracks, such as are'commonly formed by doubling material upon itself. It may also be noted from inspection of Fig. 12 that (in horizontal section) the lateral surfaces of the neck are substantially U-shaped and convexly curved toward each other, that these lateral surfaces also merge smoothly into the inner surfaces of the front and rear wings, theed'ges of the lateral margins of the neck material merging smoothly into the upper edges of the front and rear wingsas-shown in as shown at 29. and

Pig. 9. By reason of the swedging of the upper margins of the neck, as above described, the lateral surfaces of the neck are concave toward eachotherinaplaneparalleltothewingsand thus the entrance mouth 26 of each guide channel flats in width, be'ng widest at its extreme upper end, and since the margins of the neck approach each other at an acute angle and substantially meet at the point 25, these entrance moutlm or throats of the guide channels substantially merge at the latter point. Thus, as shown in Fig. 14, the neck member tap from an intermediate point of maximum lateral width both downwardly andupwardly, the end of the pull retaining member being received in the socket at the. widest part of the neck portion; Not only does the arching of the neck portion in planes transverse and also longitudinally of the slider tend to produce a maximum still.-

ness and rigidity in the sheet *metal slider; but

the upward acute taper of this member assists in eliminating the objectionable gap commonly found in fasteners of this type when the slider is in the closing position.

As indicated in Fig. 19, wherein I have illustrated end stops of "a preferred construct. on, the edges of the stringers 3 and 4 are not forced outwardly and away from each other by the interposed neck member, but above the widest part of this neck member the stringers normallylie in substantially parallel relation and may readily scams? be brought into contact so that little, if any, gap will be left at the upper end of the slider. Moreover, by reason of the dining mouths provided for the guide channels, the fastener units are enabled to enter the guide channels 'witha much smoother action than is usually possible, while the curved or U-shaped inner surfaces of the guide channels are adapted particularly to cooperate with fastener units, such as shown in Figs. 17 and 18, having smoothly rounded end portions 30-. Such rounded end portions contact with the inner surface ofthe neck throughout a substantial area so that the wear is distributed and the movement of the unit relatively to the,

neck is smoother and less harsh than when the end of the fastener unit strikes a flat surface with which it has only a line contact.

I herein refer to the neck of the slider as "tubular" for convenience in description, but with the understanding that the marginal portions of the neck material need not in all cases come into actual contact so as to form a complete tube,

since substantially the same strut-like effect is obtained if the margins of tiie'neck material do not actually abut. Furthermore, while the marginal portions of the neck material are preferably closely adjacent toeach other, if not in actual contact, at those portions which are substantially midway between the wings, so as at this part at least of the neck to form a tubular structure as above defined, such marginal portions of the neck material diverge from each other adjacent to the front and rear wings respectively so that where the neck material merges into the wings, the neck does not in fact form a complete tube nns in vertical section the neck is of substan-- tially minimum dimensions at a plane midway between the wings. radually increasing in dimension as it approaches and eventually merges into the front and rear wings, respectively, so that in I horizontal section or in plan (Fig. 12) the neck has a more or less hyperbolic contour or in,

everyday language, a contour like that of a conventional grain sheaf.

In carrying out the several steps of the process of manufacture as above referred to, I prefer to employ apparatus such as herein illustrated. This apparatus is well adapted to perform the several successive operations and in particular to keep the material under proper confinement as the material is caused to buckle and flow so as to avoid the formation of sharp angles, bends, cracks, or lines of weakness.

For performing the flrststep I prefer to use apparatus such as illustrated in Figs. 20, 21 and 22. This apparatus comprises a'die block 36 having a guide slot 37, of appropriate width-toreceive "a strip 38 of the sheet material from which the slider blanks are to be formed. The .die a block has an orifice or cavity 39 contoured to correspond to the outline of the desired blank B and with which the punch 40 cooperates to punch out the blank from the sheets. Preferably the die block is fumishedwith a fixed stripper plate the slot 37 in any appropriate manner, for expunch is reciprocatedto cut out one blank after another from the ample, by hand, while the strip.

For performing the next step in the process, apparatus such as shown in Figs. 23, 24 and 25,

. flanged blank B.

is preferably employed. This apparatus comprises a die bed 43 carrying the fixed die 44 having the orifice or cavity 45 contoured to correspond to the flanged blank B as shown in Fig.

' 3, the upper surface of the die bed having a slot for the reception of the tongue member 15 of the blank. Within the orifice or cavity 45 is arranged a die pad 46 supported upon springs 4'7 and preferably having upstanding ribs 48. A punch 49 cooperates with the die to turn up the lateral flanges 18 and 19 on the front and rear wings of the blank, the edges of the die cavity beingrounded as shown at 50 so as to obtain the desired bending of the material of the blank without cutting the latter. The lower face of the punch 49 is furnished with slots 51 complemental to the ribs 48 on the die padand adapted to operation I prefer to employ devices such as illustrated in Figs. 26, 2'7 and 28. These devices comprise a die bed 53 carrying the die 54 provided with the gauge 55 having an opening adapted to receive and properly to position the The die has a cavity 56 of a width substantially equalling the front to rear thickness of the completed slider body. A punch 57,-mounted in a holder 58, cooperates with the die 54. The punch 57 has a central portion 59 of a thickness substantially equalling the distance between the inner-edges of the side flanges of the completed slider body, and also haslateral thicker portions 60 togive it sufficient strength. The bottom of the cavity 56 in the die is furnished with a smoothly curved rib 61 and. the lower edge of the punch is provided with a recess 62 (Fig. 29) curved correspondingly to the curvature of the rib 61. The .punch holder is also-provided with a member 63 adapted to engage the tongue 15 of the blank and to turn the latter downwardly substantially at right angles to the front face of the front wing as indicated at 21, Fig. 4. The gauge 55 has a slot adapted to receive the turned down tongue 15.

The slider blank-B, Fig. 3, is placed in the opening in the gauge plate 55 and the punch is moved downwardly thereby bringing thefront and rear wings into substantially parallel relation andbending the tongue at right angles as just referred to. During the last part of the downward movement of the punch, the curved recess'62 coperateswith the rib 61 to indent the neck of the slider transverselyas-shown at 20, Fig. 5.

The next step in the process is carried out by the use of the apparatus shown in Figs. 30 to 33, inclusive. This apparatus comprises the die bed -.63 provided with the central part 64 carrying the pair of cap plates 69 and '70 secured to the die bed 63 retain the slider jaws 67 and 68 in operative position within their guide slots.

The die bed is also furnished with a transverse recess 71 adapted to receive the tongue 15 which,

projects outwardly substantially at right angles to the front wing as a result of the previous operation. The recess 71 has a bottom surface 72 provided with an upstanding shoulder at 73 (Fig. 31).

A die punch 74 cooperates with the die bed in forming the slider body, the punch being carried by a shank 75 which may be secured in the reciprocating head of a suitable die press. Cam bars 76 are secured to the opposite sides of the punch 74. These cam bars move down into the opposite ends of the slots 66 as the punch descends and engage inclined surfaces 78 and 79 respectively on the outer ends of the slider jaws 67 and 68, thus simultaneously forcing the jaws toward each other.

The punch also has a downwardly projecting arbor 80 having a vertical slot 81 (Fig. 31') whose side walls are spaced apart a distance equalling the front to rear thickness of the completed slider body and whose upper end is curved or archedat 82 substantially corresponding to the transverse arch of the slider neck as indicated at 28 in Fig. 11, the arbor being, secured to the punch by means of a pin 83. The slot 81 divides the lower part of the arbor 80 into spaced prongs, the prong 80 which is at the left side of the recess as viewed in Fig. 31, being slightly shorter than the other prong. The lower edge of the shorter prong 80 is substantially straight 105 and horizontal but has rounded comers and is adapted to cooperate with the surface '72 and shoulder 73 of the die block in bending the free end of the tongue 15 at the point 22.

The under side of the punch 74 is furnished 110 with a slot 84 (Fig. 33) which receives the upper ends of a pair of swinging arbors 85 and 86 which are pivotally secured to the punch 74. The lower portions of these arbors are of substantially the size and shape ofthe opposite 115 guide channels of the completed slider body and these arbors are furnished with outstanding fins 87 and 88, respectively adapted to extend between the opposed flanges 18 and 19 of the slider body so as to maintain a proper spacing of the flanga 126 during the shaping operation. Springs 89 and 90 tend to swing the lower portions of the arbors 85 and 86 away from each other, but such movement is limited by abutment surfaces at the upper ends of the arbors.

In using the apparatusof Figs. 30 to 33 the punch 74 is first lifted and the embryo slider of the shape shown in Figs. 4 and 5 is disposed in the die with its lateral edges engaging the inner surfaces of the jaws 67 and 68 and with 130 the tongue 15 resting in the slot '11, while the arbor 65 projects up into the lower part of the slider body' and substantially fills the latter. The punch is now moved downwardly, project mgthe lower ends of the arbors 85 and 86 into the opposite channels respectively of the slider body, the fins 8'7 projecting between the edges of the flanges 18 and 19. The shorter prong 80" of the arbor 80 engages the tongue 15 and bends it at 22 while the arched surface 82 of the arbor 14., 80 engages the neck of the slider part. As the arbor moves downwardly the cam.members '76 force the jaws 67 and 68 inwardly thereby buckling the slider body and making it narrower transversely while at the same time the surface 82 of the arbor presses down upon the neck of the slider so as further to indent the neck material and thereby to deepen the recess 20 previously formed therein and producing a deep fold depending between the wings, the result of the several concomitantly acting forces being to narrow the slider laterally and to decrease its height as shown in Fig. "I, as compared with Fig. 5, but without stretching the metal of the neck so as substantially to thin it.

After this buckling operation has been completed by the apparatus just described, the pull P die block 91 having a cavity shaped to receive the slider body and the pull retaining loop formed from the tongue 15, the pull tab 10 resting upon the upper surface of the die block while the extreme end 17 of the tongue projects into a recess 92 of the die block.

A reciprocating punch 93 cooperates with the die block and carries a bending arbor 94 (Fig. 35) adapted to engage the end 17 of the tongue and to bend its end down against the rear wing as shown in Figs. 13 and 35. The punch also has a. slot 95 in its under surface within which the pp r ends of a pair of swinging arbors 96 and 97 are pivotally supported, a spring 98 tending to swing the arbors away from each other when the punch is raised. Each of the arbors 96 and.

97 has a lower end portion 99 adapted to enter one of the slider channels, the inner edge of each arbor having a cam surface 100 (Fig. 34) adapted to swedge the extreme lateral edge portion of the neck material inwardly andover the part 16 thereby to lock the part 1'1 in fixed position. By this means the extreme lateral edges of the neck material are turned and brought into substantial contact at 25 (Fig. 14), the inner edges of the arbors 96 and 97 being smoothly curved and adapted to impart the desired concave curvature to the neck at the entrance to the slider channel.

During the operation of forming the slider body as above described the material is supported andconi'ined substantially at all points so that the material is constrained to flow in the desired direction and to the exact desired extent, the arrangement of parts being such that the material at the neck flows smoothly without fracture or abnormal disturbance of its fibrous structure thereby producing an arched tubular neck or strut merging" smoothly into the substance of the wings. 'The result is that the slider strongly resists forces tending to separate the free ends of the wings, so that the. slider body thus constructed has a strength, as .determined'by test, very much greater than that 'of previous con-'- structions,.even when the latter are made from material from 25 to 35 per cent thicker.-

It is to be noted that the dimensions of the punches and dies and associated parts which are 4 v employed are-such that when the slider is confinedbetween the operating parts during the buckling operations it is not pinched, so as to be thinned down at any point, as is the case with most previous types of bending and forming dies used for similar purposes. Thus, when the slider of Fig. 4 is placed in the die shownin Fig. ,33 it fits snugly but freely therein. The bottom arbor which is of the exact size in horizontal section, of the ,interengaging fastener units with hich the slider is intended to cooperate, fits closely but freely in the lower end of the slider body; tbearbors and 86 close y' 1,ess,727

fit but do not bind in the channels of the slider; while the two prongs of the arbor 80 engage the outer surfaces of the .respective wings with a free sliding fit so as to support the wings against spreading as the surface 82 of the arbor forces the neck material downwardly.

In Figs/36 and 37 I have illustrated by diagrams my present theory as to what takes place when the metal of the neck is indented solely by downward pressure, as has heretofore been proposed, as contrasted with the action when the downwardly applied force is assisted by inwardly directed lateral forces.

Thus, in Fig. 36, assuming that the part 144 is the neck portion of an embryo slider such as 9 shown in Fig. 5, and that the lines xy-ry represent the vertical planes of the lateral edges of the neck material,-if the downward force F be, applied to the central part of the neck 144 so as to indent the neck material downwardly, as indicated at 145 without changing the relative positions of the planes 31l 1l, the material of the neck must necessarily stretch and become substantially thinner,tending to stretch non-uniformly, becoming thinnest at points 146 and'14'! intermediate the upper and lower parts of the neck material. It may be noted that the parts of minimum thickness occur at substantially that portion of the neck where maximum stress is encountered in resisting separation of the wings during use.

On the other hand, if, as illustrated in Fig- 37,while the downward force F is applied for indenting the neck material, other forces 1'' and F respectively, are caused concomitantly to -or appreciable thinning of the side walls 149 and 150, it being noted in this connection that in proceeding in this way, the force F may be of less intensity than the force F acting alone. Apparently the inward movement of the sides of theneckservesinasens'etofeedinmaterialm in such a way as to avoid depletion and thinning of the downwardly flowing metal. Thus the walls of the completed fold, (below their extreme upper edges) are of substantially the same thickness as that of the original blank, and are uniformly thick in transverse section and devoid of weakened areas-thedistributed stresses employed in the process being well adapted to harden the metal by cold working without producing incipient cracks or fractures, so that the 139 neck is very strong and stifl', and well able to resist stresses applied thereto. It is to be understood that the diagrams of Figs. 36 and 37 are merely illustrative of' a theory and are not in- 9 tended to show exact dimensions or relations of 1''5 parts. L'

In Figs. 15 and 16 a modified construction .of pull retaining element is shown, such pull re'- taining element consisting of a separate and independent member comprising the elongate por- 4 tion 15' adapted to receive the pull tab and a toe portion 31 at its lower end which is adapted to enter an opening in a lug 32 projecting forwardly from the lower end of the front wing 13 of the slider body. The upper end of the'member 15" is furnished with an arm 33 having a shoulder at 34 adapted to engage the front wing and a downturned portion 35 at its rear end adapted to overlap the rear wing, it being understood that the part as is disposed in the socket in the neck of tion of Fig. 1. Moreover, when I refer to the lateral margins of the neck I intend to indicate the right and left-hand edge portions of the neck as shown, for example, in Fig. 14, such portions being formed from the free margins of the neck portion 14 of the blank shown in Fig. 2. Moreover, when I refer to a transverse section or plane, I intend thereby to indicate a section or plane substantially parallel to the planes of the front and rear wings.

While I have herein illustrated certain desirable embodiments of the invention by way of example, I wish it to be understood that the invention is not necessarily limited thereto, but that modifications thereof, variations in material and dimensions, and the substitution of all equivalents may be made without departing from the spirit of the invention.

I claim:

1. That method of forming a sheet metal slider of the class described which comprises as steps preparing an embryo slider having substantially parallel front and rear wings a neck uniting the wings, working the material of the neck inwardly to form a depression extending from front to rear of the slider and, while so working the neck material, buckling the slider transversely to prevent thinning of the material of the neck- 2. That method of forming a slider of the class described which comprises as steps preparing a blank having front and rear wing portions and a connecting-neck portion, bringing the wing portions into substantially parallel relation while forming in the neck portion a shallow concave recess extending from front to rear,' thereafter confining the resultant embryo slider substantially at all points, and, while so confining it, applying opposite and inwardly directed forces to its lateral edges such as'to narrow the slider body while concomitantly applying force to deepen the recess in the neck.

3. That method of forming a slider of the class described which comprises as steps preparing an embryo slider having substantially parallel front and rear "wings united by a neck, confining the slider so as to prevent movement of the wings toward or away from each other, narrowing the slider by the applicationof force to its lateraland rear wings united by a neck, and narrowing the slider by the application of laterally directed forces while concomitantly decreasing the height of the slider by the application of longitudinally directed force.

5. That method of forming a slider of the class described which comprises as steps, preparing an embryo slider having substantially parallel front and rear wings and a neck uniting the wings, applying pressure to the neck so as to form a depression therein extending from front to rear, the bottom of thedepression being concave in a transverse plane and convex in a front to rear plane and, while so applying pressure to the neck, applying force in such a way as to narrow the slider transversely.

6. That method of forming a sheet metal slider of the class described which comprises as steps preparing an embryo slider from sheet material, said slider having a neck uniting flanged'front and rear wings defining convergent channels, and, while maintaining unchanged the spacing of the wings and their flanges, applying pressure to the lateral margins of the slider in such a way as to narrow the upper part of the slider and to buckle the material of the neck.

7. That method of forming a sheet metal slider of the clam described which comprises as steps preparing an embryo slider from sheet material, said slider having a neck unitingfianged front and rear wings defining convergent channels, and, while confining the wings both interiorly and exteriorly, decreasing the width of the up per part of the slider by force applied to its lateral edges thereby to-buckle the neck material.

8. That method of forming a sheet metal slider of the class described which comprises as steps preparing an embryo slider from sheet material, said slider having a neck uniting flanged front and rear wings defining convergent channels, and, while confining the'wings tomaintain them in substantially parallel predetermined spaced relation, concomitantly applying force to the lateral edges of the slider and to the neck thereof whereby to. buckle the neck and to arch it in directions substantially at right angles to each other.

9. That method of forming a sheet metal 5 slider of the class described which comprises as steps preparing an embryo slider from sheet material, said slider having a neck uniting flanged front and rear wings defining convergent channels, and, while confining the wings both inter- 120 nally and externally, applying force in such a way as to narrow the upper portion of the slider body transversely and, to cause the material of the neck to become arched both transversely and from front to rear.

10. That method of forming a sheet metal slider 'of the class described which comprises as steps preparing an embryo slider from sheet material, said slider having a neck uniting flanged front and rear wings defining convergent channels, and, while maintaining the wings in paral-' lel predetermined spaced relation decreasing the width of the upper part of the slider by force applied to its lateral edges while depressing the neck thereby to form a transversely concave recess in'the neck, and thereafter swedging the margins of the neck to bring said edges substantially into contact.

, 11. That method of forming a sheet metal slider of the class described which comprises as steps preparing an embryo slider from sheet material, said slider having a neck uniting flanged front and rear wings defining convergent chan-' nels, applying force in such a way as to buckle the material of the neck and to produce a transversely concave recess therein, and thereafter swedging the margins-0f the neck to turn such margins and to bring them substantially into contact.

- 12. That method of forming a sheet metal 154:

" come arched in .planes substantially at right .angles to each other whereby to provide a still,

rigid strut between the wings.

"13. That method of forming a sheet metal slider of the class described which comprises as steps preparing an embryo slider from sheet material, said slider having a neck uniting flanged front and rear wings defining convergent channels, and applying force to the neck and to the lateral edges of the slider in such a way as to buckle the neck material without thinning the later, whereby to form a stiil, rigid strut having concave outer surfaces merging smoothly into the inner surfaces of the respective wings.

14. That method of forminga sheet metal slider of the class described which comprises as steps preparing an embryo slider from sheet material, said slider having a neck uniting flanged front and rear wings defining convergent channels, and concomitantly applying force to the neck and to the lateral edges of the slider whereby to buckle the neck and form a trans versely concave recess in the latter while imparting to the inner surfaces of the neck an upwardly arched contour in front to rear sec tion;

15. That method of forming a sheet metal slider of the class described which comprises as" steps preparing-an embryo slider from sheet material, said slider having a neck uniting flanged front and rear wings defining convergent channels, applying force to the neck and to the lateral edges of the slider whereby to buckle the neck and form a transversely concave recess in the latter while imparting to the inner surfaces of the neck an upwardlyarched contour in front to rear section, and thereafter causing the margins of the neck material to move into engagement thereby to provide 1 transversely flaring mouths for the respective channels of the slider.

16. That method of forming a sheet metal slider of the clam described which comprises as steps preparing an embryo slider from sheet material, said slider having a neck uniting front and rear wings defining convergent channels, concomitantly applying longitudinally and laterally directed forces to buckle the neck and form a transversely concave recess in the latter while imparting to the inner surfaces of the neck an upwardly arched contour in front to rear section, and thereafter applying force to the lateral margins of the neck to bring said margins into contact and to cause the neck to taper upwardly substantially to a point defining the extreme upper end of the slider.

17. That method of" forming a sheet metal slider of the class described which comprises as steps preparing an embryo slider from sheet mainner surfaces of the neck an upwardly arched contour in front to rear section, inserting one end of a pull retaining member in said recess, and

forcing the margins of the neck over the end of said pull retaining member to anchor the latter in position.

18. That method of forming a sheet metal slider of the class described which comprises as steps preparing an embryo slider from sheet material, said slider having a neck uniting front and rear wings defining convergent channels, concomitantly applying longitudinally and laterally directed forces to buckle the neck and form a trans-" versely concave recess in the latterwhile impartin v to the inner surface of the neck an upwardly arched contour in front to rear section, and swedging the margins of the neck to provide transversely flaringmouths for the slider channels. v

19. That method of forming a sheet metal slider of the class described which comprises as steps preparing an embryo slider from sheet material, said slider having a neck uniting flanged front andrear wings defining convergent channels, applying force to the neck and to the lateral edges of the slider whereby to buckle the neck and form a transversely concave recess in the latter while imparting to the inner surfaces of the neck an upwardly arched cont-our in front to rear section, and so swedging the margins of the neck as to provide transversely flaring mouths for the slider channels, said mouths substantially merging at the extreme upper end of the slider.

20. That method of forming a slider of the class described which comprises as steps preparclass described which comprises as-steps preparing from a sheet metal blank an embryo slider having substantially parallel front and rear wings united by a neck, and forming the neck to pro vide a deep depending fold by the concomitant application of downward and inward lateral pressure, thereby maintaining a thickness of material at the smallest cross section of the neck substantially as great as that of the original blank.

22. That method of forming a slider of the class described which comprises as steps preparing from a sheet metal blank an embryo slider hav ing substantially parallel front and rear wings united by a neck, and so applying pressure to the neck material as to form a deep depending fold while narrowing the wings transversely at a rate sufiicient to prevent thinning of the neck during formation of the fold.

23. That method of forming a slider of the class .described which comprises as, steps preparing from a sheet metal blank an embryo slider having substantially parallel front and rear wings united by a neck, and so applying pressure to the neck material as to provide a deep depending fold while bringing the opposite edges of the neck material nearer together, thereby to provide a hollow strut-like member whose walls have aminimum thickness substantially as great as'that of the original blank. I GEORGE E. PRENTICE. 

